P38A petrol v8s

[badfluffy]

ok last rover v8 i rebuilt was the 3.5 so my question is how different other than cc is the Thor motor to the old 3.5, and the gems, reason for asking is the thor has no oil pressure but a friend has a spare gems, is it just a matter of switching over the intakes ect ?

 

[kermit_rr]

The blocks on the 3.9 4.0 and 4.6 are the same, bigger bore than the 3.5

 

[badfluffy]

The blocks on the 3.9 4.0 and 4.6 are the same, bigger bore than the 3.5

so from that i take it i can just simply swap over all the external parts and hopefully save a good car

 

[kermit_rr]

That's my understanding.
The 3.9 and 4.0 are the same cc. The 4.6 has a different stroke to gain the extra cc
I think the heads are all the same

 

[badfluffy]

Monday just looked a little brighter

 

[pwood999]

Best to keep the discussions to one thread ?

But start with draining fluids & taking front cover off to check the oil pump. If it's ok, prime it, and put fresh oil in the engine & try again.

 

[Ratae]

Does the oil warning light come on when ignition is turned on?
Oil pressure sender faulty?

 

[badfluffy]

Best to keep the discussions to one thread ?

.

i split the engine question off because i needed to understand what the differences were in the blocks

 

[DanClarke]

Thor Motronic was allegedly an improvement over the GEMS injection system.
Before going to a lot of swap-over work I would try what @Datatek said and spin it over for a fair bit with the plugs out and plenty of oil showing on the dipstick and see if you can wind some oil pressure up.
Didn't a new oil pump used to entail packing it with vaseline or the like in order to get it to prime and suck oil up from the sump?
Standing for a long-long time will mean its as dry as a bone. I don't know it you can get oil into the pump from the reverse direction to prime it, so spinning it up on the starter is all that's left.

 

[tomcat59alan]

Thor Motronic was allegedly an improvement over the GEMS injection system.
Before going to a lot of swap-over work I would try what @Datatek said and spin it over for a fair bit with the plugs out and plenty of oil showing on the dipstick and see if you can wind some oil pressure up.
Didn't a new oil pump used to entail packing it with vaseline or the like in order to get it to prime and suck oil up from the sump?
Standing for a long-long time will mean its as dry as a bone. I don't know it you can get oil into the pump from the reverse direction to prime it, so spinning it up on the starter is all that's left.

We used to fill the pump with oil during rebuilding, @Saint.V8 had an oil pressure problem,I'm sure there's a write up in the Technical archive , turned out to be the O ring on the oil pickup pipe if memory serves me correctly

 

[DanClarke]

We used to fill the pump with oil during rebuilding, @Saint.V8 had an oil pressure problem,I'm sure there's a write up in the Technical archive , turned out to be the O ring on the oil pickup pipe if memory serves me correctly

Yes @tomcat59alan I remember the post and his "Aha!" moment being described.

 

[badfluffy]

the petrolam jelly trick has already been suggested by the guy who is giving me the spare engine

 

[marjon]

I seem to remember the front cover being an issue but cant remember why.

But did a quick goggle and came up with this may throw some insight P38 Gems 4.6 from Thor 4.0 conversion | LandyZone - Land Rover Forum

But as you will have both standing in front of you it may be easier to tell.

J

 

[badfluffy]

so may not be as easy as first thought

 

[Grrrrrr]

ok last rover v8 i rebuilt was the 3.5 so my question is how different other than cc is the Thor motor to the old 3.5, and the gems, reason for asking is the thor has no oil pressure but a friend has a spare gems, is it just a matter of switching over the intakes ect ?

In theory yes but I think the Thor has some subtle differences. I don't think the threads changed but I think some of the Thor nuts/bolts were metric where they were imperial on the GEMS. Not sure about stud patterns and mounting points. Pretty sure some of the sensors were different too although I am sure it could be fettled to work. Might be wrong as I haven't had a Thor engine apart but I wouldn't expect a hassle free swap.

 

[pwood999]

Key differences I know of: (apart from the obvious like manifolds & coils)

• Camshaft sprocket gap are different
• Crank sensor uses different flywheel teeth and different number of positions.
• Engine wiring loom
• BECM settings

 

[badfluffy]

Key differences I know of: (apart from the obvious like manifolds & coils)

• Camshaft sprocket gap are different
• Crank sensor uses different flywheel teeth and different number of positions.
• Engine wiring loom
• BECM settings

well 2 3 and 4 wont be an issue if the original parts can swooped over

 

[marjon]

I think you need to do a little bit more investigation on your original engine. to establish what it is if its the oil pump then. And as that has to come off to get to the different camshaft sprocket to change then you may aswell sort the 1 you have.

If the front covers have to be changed it maybe pointless as that houses the oil pump.

J

 

[badfluffy]

once ive got it parked in a corner out the way i will start investigating, at the moment im just investigating possibility's if the engine is toast

 

[tomcat59alan]

so may not be as easy as first thought

You could always remove the oil pressure switch and pump oil in from an oil can and see if it primes the pump.